Photographic emulsion containing neothiazolocarbocyanines



Patented Aug. 7, 1934 UNITED STATES PHOTOGRAPHIC EMULSION CONTAINING NEOTHIAZOLOCARBOCYANINES Leslie G. S. Brooker, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New York Application June 30, 1931, Serial No. 548,026

Claims.

This invention relates to a new composition of matter and particularly to a new class of photographic sensitizing dyes known as neothiazolocarbocyanines vand photographic emulsions con- 5 taining them.

Most ordinary photographic emulsions are comparatively indifferent to those colors of the spectrum of longer wave-length and for that reason various types of sensitizing dyes have been suggested for use. These may be incorporated in v'the emulsion, or employed in a sensitizing bath, in which the photographic iilm or plate is bathed. Many cyanine dyes ha-ve been described for this, purpose containing the benzothiazole nucleus. Dyes containing the naphthothiazole nucleus are described in my applications, Serial Nos. 337,177 filed February 2, 1929 (Patent No.

1,846,300), 435,104 filed March 12, 1930 (Patent No. 1,846,301), 435,105 led March 12, 1930, and l dyes containing the thiazoline nucleus aredescribed in my co-pending application Serial No.

460,548 led June 11, 1930.

An object of the present invention is to provide a process for the preparation of photographic sensitizers of a new type containing the thiazole nucleus. These dyes may be termed neothiazolocarbocyanines, by analogy with, neocyanine, which is thought to contain a similar linkage connecting its three heterocyclic nuclei. Another object of the invention is to provide such photographic sensitizing dyes as may be added to photographic emulsions or coated thereon as an overcoating, thereby increasing the spectral sensitiveness of the emulsion. A further object is to provide a gelatino silver halide' emulsion in which is incorporated one or more of the new dyes disclosed herein and a photographic element comprising such an emulsion. Other objects will hereinafter appear.

The thiazole ring is usually numbered in the following manner, and this system of numbering is used in the present application:

ethylorthoformate and pyridine underappropriate conditions yield as a principal product thiazolocarbocyanines.

If trialkyl ortho esters of carboxylic acids other than formic acid are employed in the condensation, thiazolocarbocyanines are obtained with substituent groupings attached to the central carbon atom of the three-carbon carbooyanine chain. For instance triethylorthopropionate yields 7ethylthiazolocarbocyanines.` These dyes 65 are fully dealt with in my co-pendingapplication Serial No. 619,962 filed June 29, 1932. l

The Z-methyl thiazoles also yield such dyes as thiazoloiso-cyanines l'and thiazolo-vf-cyanines. These are dealt with in my co-pendingapplication Serial No..619,960 led `June 29, 1932.

In the present case, dialkylsulfates and more especially-alkyl p-toluenesulfonates are used for the preparation of the thiazole alkylquaternary salts, and these when treated with an excess of ethyl orthoformate in anhydrous pyridine yield the neothiazolocarbocyanines of the instant application in preponderating amounts. A Small amount of simple thiazolocarbocyanine frequently accompanies the neothiazolocarbocyanine, but as a rule the latter dyes are less soluble than these simple thiazolocarbocyanines and can readily be isolated in a pure state.

Analytical results indicate that the molecule of neothiazolocarbocyanine contains vthree thiazole nuclei, in two of which the nitrogen atoms are in the pentavalent state. The dye is probably represented by one of the following formulae:

I A s s\ /ll \C1'\ s 7 o /1 5C 4, 2'c=oH-c=cH-o 2\ 4 B/C\,.}/ H. \/./"\B

sf 2N X 5 4l 11 A B s A 100 N35/'VX s 7 o /1\5C/ (L, o=oHo=cHo2 4 B/ \J/ fn C\B l, in R X los 5 4C by \B 11o In these formulae A and B represent univalent atoms or groupings such as hydrogen, alkyl or aryl; R stands for alkyl and X represents a suitable acid radical.

The general name for I is 3,3'dialkyl7 (thiazyl 2 alkyl salt) methyl thiazolocarbocyanine salt and that for II is 3,3dialkyl7 [(thiazyl2 alkyl salt) vinyll-thiazolocarbocyanine salt. consideration of atoms or groups A and B is omitted for the sake of simplicity. Since these new dyes are believed to be structurally related to the known dye neocyanines, it is logical to call them "neothiazolocarbocyanines been done herein.

The quaternary alkyl thiazyl group which is linked through the vinylene chain in the above formulae, has the alkyl group and the acidic radical both linked to the nitrogen atom of the thiazyl nucleus. This nitrogen atom is numbered 3 but since it is the only position in this thiazyl nucleus for such linkage, the number need not appear in the name of the dye.

In Formula Lone molecule of ethylorthoformate is supposed to have reacted with three molecules of quaternary salt, whilst Formula II may be arrived at by supposing that two molecules of ethylorthoformate react with three molecules of the alkyl quaternary salt. For various reasons, it is thought that Formula II isv the more probable one, and the analytical evidence favors it in most cases. In any event, the utility of my invention is not affected by theoretical considerations relating to the exact structure of the molecule.

I will now give several examples for preparing various neothiazolocarbocyanines from the corresponding 2-methylthiazoles. However, it will be understood that they are merely representative of a great number of methods in which the proportions given and the equivalents used may vary for the particular type of dye required. My invention, therefore, will not be restricted thereby except as indicated in the appended claims.

PREPARATION oF NEoTnIAzoLocARBocYANINEs Step I Ihe thiazole base containing a reactive methyl group is first converted into an appropriate alkyl quaternary salt, by heating withffor instance, an alkyl sulfonic ester, such as an alkyl p-toluene sulfonate. 'Ihe dialkyl .sulfates may also be 'employed, but the yields are usually lower.

-A and B are hydrogen atoms or substituent atoms or groups, R stands for alkyl andX stands for a suitable acidic radical such as p-toluene sulfonate (-O.SOz.C1H'1) or alkyl sulfate (--O.SO2.OR)

Step II l' '.The thiazole alkyl quaternary salt is heated In these two general names which has.

' named in accordance with my preferred general mation occurs. This is most probably represented as follows:

ont

c-c Etoont 0H o P 'd 80 (I L; N/ H. r-

(rlllll B/ R/ \X R/ \X ont H- ont OEt im S/ \/R 9.0 \C=C \X A B s s \C/ \C/ g C=ono=cHc \N/ H \N/ B Il B+6EOH+C5H5N,HX R EH R x 100 R S/ \N/ \C=C/ \X A B (In the above formulae, Et represents the ethyl group 02H5). The dye may be isolated at this stage or it may be isolated as a more sparingly soluble salt in Step III.

step' III 11 This is a simple step and consists of dpuble decomposition. The reaction mixture, concentrated'or otherwise, or the solution of the dye in some other solvent is treated with an aqueous solution of an alkali salt of the acid whose anion it is desired to introduce into the dye. For instance, the p-toluene sulfonate of a dye may be treated with an aqueous solution of potassium iodide or sodium iodide or ammonium bromide. Thisv alkali salt is conveniently employed in considerable excess. The dye iodides, for example,

- are usually fairly insoluble in cold aqueous solutions containing excess of inorganic iodide, and may therefore be conveniently obtained by ltration in the usual way.

Step IV Formula II:

ExAMrLE I I odz'de of the neothz'azolocarbocyanne from 2- methylthiazole metho-p-toluenesulfonate 3,3'.- dzmethyl-7 [-(thz'azyZ-Z methzodde) -vinyllthz'azolocarbocyam'ne iodide 9.9 g. 2-methylthiazole (3 mols.) was heated vwith 18.6 g. methyl p-toluenesulfonate (3 mols.)

on the steam bath. Addition took place rapidly 15g and solidication appeared 'to be complete in about ve minutes. The solid quaternary salt was dissolved in 150 cc. boiling dry pyridine and 16.5 cc. ethyl orthoformate (3 mols. 50% excess) added and the whole refluxed for rive hours. On standing in the cold, crystals of the neothiazolocarbocyanine metho-p-toluenesulfonate separated. These were ltered oir and washed with cold pyridine and then dissolved in boiling methyl alcohol and an aqueous solution of excess of potassium iodide in warm distilled water added and the mixture stood aside to crystallize out. The iodideof the dye so produced was filtered off and washed and the more; soluble neothiazolocarbocyanine was removed by treatment with a hot mixture of acetone and methyl alcohol. The dye was puried by crystallization from methyl alcohol and was nally obtained as a dull purplish-black felted crystalline mass and gave a Violet solution in methyl alcohol.

EXAMPLE II Iodz'de of the neotliiaeolocarbocyanine from 2- methylthzazole ethoptoluenesulfonate 3,3'- diethyZ-7- l'- (thaeyl-Z ethiodide) -mnyll -thz'- azolocarbocyanine iodide 9.9 g. Z-methylthiazole (3 -mols.) was heated with 20 g. ethyl p-toluenesulfonate (3 mols.) on an oil bath at 117-120" C.' overnight. The crude Z-methylthiazole etho-p-toluenesulfonate was boiled under reflux with 40 cc. anhydrous pyridine and 22.2 cc. ethyl orthoformate (4 mols. 100% excess) for ve hours. Most of the solvent was removed by concentration in vacuo and the residue Was stirred with hot distilled water and an excess of potassium iodide was added and the Whole well mixed and stood aside to crystallize out. The dye was then filtered and washed. The residue was then dried and consisted of greenish-bronze crystals apparently mixed with darker dull green crystals. The dye was boiled with acetone and ltered hot but the filtrate was quite bluish and little or no crimson thiazolocarbocyanine seemed to be present in the preparation: The dye was crystallized from methyl alcohol and gave beautiful greenish-bronze plates which imparted a violet coloration to methyl-alcohol.

EXAMPLE III Iodz'de of the neothiasolocarbocyanine from 2,4-

dz'methylthz'azole metho-p-toluenesulfonate 3,4, 3' ,4 tetramethyl 7 [-(4-methylthiazyl 2 methiodide) -vinyll -thazolocarbocyam'ne iodide 11.3 g. 2,4-dimethylthiazole (3 mols.) was heated on an'oil bath at 115 C. with 18.6 g. methyl p-toluenesulfonate (3 mols.) for about an hour, solidication occurring within the first five minutes or less. The quaternary salt so obtained was refluxed for 41/2 hours with pyridine (60 cc.) and 22.2 cc. ethyl orthoformate (4 mols.) During the reaction much solid appeared. The reaction mixture was allowed to cool overnight and the p-toluenesulfonate of the dye was then vfiltered off. The dye was converted into the iodide by boiling it with methyl alcohol and slowly stirring in a hot solution of potassium iodide in water. The whole was allowed to cool, and was then filtered and the dye washed. When dried,

the iodide of the dye consisted of a greenish-grey l powder. Most of the more soluble crimson thiazolocarbocyanine was removed by boiling the dye with a mixture of methyl alcohol and acetone and v alcohol.

lteringhot'. The residue was recrystallized from methyl alcohol and the dye, when air-dried, consisted of a felted mass of greenish-brown slender hairs and gave a violet-blue solution in methyl EXAMPLE IV Iodz'de of the neothiazolocarbocyanine from 2,4-dz'methylthz'azole metho-methylsulfate 3,4, 3,4 tetramethyl 7 (4 methylthiazyl 2 methzodide) -vinyll -thiazolocarbocyam'ne iodide 12.6 g. dimethylsulfate (3 mols.) was placed in a ask provided with a reflux condenser and 11.3 g. 2,4-dimethylthiazole (3-mols.) added in small portions down vthe condenser. This addition was accompanied by much heat evolution. The product was heated for a further hour at about 115 C.

The crude quaternary salt was refluxed for 41/2 95 hours with 60 cc. pyridine and 22.2 cc. ethyl hot distilled water. The dye was ltered oi when cold and washed. The air-dried dye consisted of EXAMPLE V Iodide of the neothiazolocarbocyam'ne from 2,4- dimethylthiazole etho-p-toluenesulfonate 4,4- dimethyl 3,3' Methyl-7 [-(4-methylthiaeyl- 2 ethiodz'de) -m'nyll -thz'aeolocarbocyamne iodide 11.3 g. 2,4-dimethylthiazole (3 mols.) was heated overnight at 115-120 C. with 20 g. ethyl p-toluenesulfonate (3 mols.). The crude quaternary salt, which was a light brown viscous liquid, was rei'iuxed for 5 hours with 40 cc. pyridine and @.2 cc. ethyl orthoformate (4 mols.). The reaction mixture was concentrated in vacuo and the residue mixed with hot distilled water and an excess of potassium iodide added. The dye was allowed to crystallize out and was then filtered oi and washed. The air-dried dye consisted of small, dark bluish-green crystals. The dye was boiled with methyl alcoholand stood to cool somewhat I and was then filtered before it was quite cold. 135 The dye left on the iilter was almost pure normal thiazolocarbocyanine and consisted of small purple needles which gave a crimson solution. The mother liquor .was concentrated somewhat and was then cooled in a freezing mixture. 140 Bluish-green crystals of the neothiazolocarbocyanine iodide were obtained. The mother liquor and Washings were again concentrated and a third crop of crystals obtained, and similarly a fourth and iifth crop. 'Ijhese crops consisted of 145 tolerably pure neothiazolcarbocyanine.

The dye was. crystallized from methyl alcohol into beautiful greenish needles which became dull on drying and which gave a violet-blue solution in methyl alcohol.

EXAMPLE VI Iodde of the neothiaeolocarbocyanne from 2- methyl-4-phenylthz'azole metho-p-toluenesulfo'nate 4,4' diphenyl 3,3'dimethyZ-7[ (4- phenyZthiaayZ-Z A'methodide) -vinyll -thiazolocarbocyanine iodide became crystalline and was cooled and filtered.

The air-dried dye consisted of a purplish-brown crystalline powder. The crimson normal thiazolocarbocyanine was removed by boiling with a mixture of methyl alcohol and acetone. The dye was then recrystallized from methyl alcohol and when dried consisted of a dull greenishbrown powder. The color -of the methyl alcoholic solution was blue.

EXAMPLE VII Iodide of the neothiazolocarbocyanine from 2- methyZ-4-phenylthazole etho-p-toluenesulfonate 4, 4-diphenyZ-3, 3diethyl7[(4phenyl -thiagyZ-Z `ethzodide) -m'nyll -thazolocarbocyanine iodide',l

8.8 g. of 2-methyl-4-phenylthiazole (3 mols.)

was heated for 65 hours at 110-125" C. with 10 g. ethyl p-toluenesulfonate (3 mols.). The product, which was-a lightjbrown viscous liquid, was

reuxed for 5 hours with pyridine (20 cc.) and 11 cc. ethyl orthoformate (4- mols.). The dye was precipitated as the iodide by adding a hot solution of an excess of potassium iodide in water and"stood aside to cool. The dye was filtered off and as it was somewhat tarry it was boiled with acetone, cooled, and filtered.l The dye when dried consisted of a dull bronze colored powder. The dye was boiled with a mixture of methyl alcohol and acetone and filtered hot,'but the solution was quite blue, as though little or no normal thiazolocarbocyanine were present. The dye was nally crystallized from methyl alcohol and consisted of small coppery crystals which .gave a blue solution in the solvent.

As previously indicated and from the foregoing examples it will be observed that the neothiazolocarbocyanines are produced by the condensation of thiazole alkyl quaternary salts, containing reactive methyl groups (Z-methylthiazole alkyl quaternary salts) with ethyl orthoformate in some suitable solvent such as anhydrous pyridine. Analytical evidence suggests that 3 molecules of the quaternary salt condense together with one, or more probably two, molecules of ethyl orthoformate. However, not every salt will give suitable -yields of the neothiazolocarbocyanines inasmuch as some,- notably the iodides, give principally the normal thiazolocarbocyanines in most cases. l

The dyes may also be described as a particular type of 7-substituted thiazolocarbocyanine.` In this case the substituent is an alkyl quaternary thiazyl vinylgroup. Vinyl is CH2=CH and if one H ofthe CH2: group is replaced by an alkyl quaternary thiazyl group linked through its 2 position we get the substituent groupingi After standing to probably present in the neothiazolocarbocyanines.

The diagrammatic spectrograms constituting the accompanying drawing illustrate the regions of the spectrum to which the various types of dyes herein disclosed ,will sensitize a gelatinosilver-halide emulsio Ktand the extent of the sensitization at various `ave lengths. The figures of this drawing and the dye, the sensitizing properties of which each of the Figs. 1 to 6 illustrates, are listed, respectively, at the top of each spectrogram. These figures were all taken from silver. bromide emulsions in which the respective dyes were incorporated as herein described; corresponding ones taken from chloride emulsions vary somewhat but areromparable in region and density. I

In the preparation of emulsions containing these photographic sensitizers, it has been found that the dye may be dissolved in methyl alcohol and a volume of solution diluted with water and containing from 5 to 100 milligrams of dye added to 1000 cc. of, for instance a owable photographic gelatino-silver-halide emulsion, which may then be coated upon a suitable glass or cellulose derivative, transparent support and allowed to dry, the details of which are well known to emulsion experts. While it may not be necessary to add some of the sensitizers in a large amount, it may be necessaryto add others in amounts larger than those given above; generally about 10 to 20 milligrams is suicient to obtain the maximum sensitizing effect with a dye having good sensitizing power. The more powerful dyes, however, may require much less. The regulation or adoption of the most economical proportions will be apparent to those skilled in the art upon observing the sensitizing power of the particular dye for the particular emulsion in question. The above examples are, therefore, illustrative and not to be understood as limiting the invention in any sense, as it will be apparent that these dyes may be incorporated by other methods in many of the photographic emulsions customarily employed in the art, such for instance as by bathing the plate or film, upon which the emulsion has been coated, in a solution of the dye in an appropriate solvent although this method of incorporating the dye in the emulsion is not to be preferred over that above described. Obviously the claims are all intended to cover any combination of these dyes with a photographic emulsion whereby the dye exerts a sensitizing elfect upon the emulsion.

A photographic emulsion in which is incorporated as above described, one or more of the new dyes disclosed herein possesses in general strong sensitivity to the green and blue green portion of the spectrum as will be observed from the accompanying drawing.

4What I claim as new and desire to secure by Letters Patent is:

1. A gelatino-silver-halide emulsion which contains a sensitizing dye having most probably the following structure Lid in which A and B represent hydrogen atoms, or aliphatic or aromatic groupings, R represents an alkyl group and X represents a suitable acid radical.

2. A photographic element comprising a supporting surface coated with a gelatine-silverhalide emulsion which contains a sensitizing dye having most probably the following structure in which A and B represent' hydrogen atoms, or aliphatic or aromatic groupings, R represents an alkyl group and X represents a suitable acid radical.

3. A gelatino-silVer-halide emulsion which contains a 3,3dialkyl'7[(thiazyl2 alkyl quaternary salt) vinyl]-thiazolocarbocyanine salt.

4. A gelatin-silver-halide emulsion which conthiazyl-2 methyl quaternary salt) vinyll-thiazolocarbocyanine salt.

10. Av gelatino-silver-halide emulsion which contains a 4,4diphenyl3,3' -diethyl-7 4phe ny1thiazyl-2 ethyl quaternary salt) vinyll-thiazolocarbocyanine salt.

LESLIE G. S. BROOKER. 

